Missing Cairo commits from libreoffice-5-1 branch

Hi,

I noticed that libreoffice-5-1 is missing a number of Cairo-related commits
that were done in Master but weren't cherry-picked into the 5.1 branch.

Functionally, I can see that SvpSalGraphics::drawAlphaBitmap is missing in
5.1.

This was implemented in:
c1774eb gtk3: implement drawAlphaBitmap for svp/gtk3 backend

and later improved in:
4fee13c gtk3: of course we have a different 1 bit mask format as well
db88445 gtk3: use cairo to do drawAlphaBitmap with scaling

I don't know if this causes any visible defects on the desktop (probably
someone would have notice if it had,) but it certainly breaks in Online
(transparent areas are rendered as black).

There are other candidate gtk3 commits that might be missing from 5.1. For
example:
ac49efd gtk3: track what needs to be implemented
3d22df1 gtk3: implement drawPolyLine for svp/gtk3 backend
872c1b7 gtk3: it's the *Original* device we care about, not the temp clip
hack devices


*Should I submit these patches to libreoffice-5-1 for review?*

Thanks,
-Ash